Calcium reacts with water to form calcium hydroxide and hydrogen gas.
Understanding the Reaction of Calcium with Water
When calcium metal (Ca) is placed in water (H₂O), a chemical reaction occurs. Unlike the vigorous reaction of alkali metals with water, the reaction of calcium is less intense. The reference material states that this reaction produces calcium hydroxide (Ca(OH)₂) and hydrogen gas (H₂).
The chemical equation for this reaction can be represented as:
Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)
- (s) indicates solid
- (l) indicates liquid
- (aq) indicates aqueous solution (dissolved in water)
- (g) indicates gas
Observations During the Reaction
The reference provides key observations about how calcium reacts with water:
- Sinking: The calcium metal sinks to the bottom when placed in water.
- Hydrogen Bubbles: After an hour or so, bubbles of hydrogen are evident, stuck to the surface of the metal. This indicates the gradual production of hydrogen gas.
- Calcium Hydroxide Formation: Calcium hydroxide is formed. This compound is sparingly soluble in water, forming a slightly alkaline solution, sometimes referred to as "limewater".
Summary of the Reaction
Here's a quick overview of the reaction components:
| Component | Description |
|---|---|
| Reactant 1 | Calcium (Ca) |
| Reactant 2 | Water (H₂O) |
| Product 1 | Calcium Hydroxide (Ca(OH)₂) |
| Product 2 | Hydrogen Gas (H₂) |
| Reaction Speed | Relatively slow compared to Group 1 metals |
| Observation | Metal sinks, H₂ bubbles appear later |
This reaction demonstrates calcium's position as an alkaline earth metal, reacting with water more slowly than alkali metals, but still producing hydrogen gas and the corresponding metal hydroxide.
